This invention concerns a process for removing liquid contaminates from a solid surface and more particularly concerns equipment for effectively washing the liquid contaminates from the surface in a minimum of space. There is a need in the art for improved methods and equipment for separating the liquid from liquid contaminated surfaces. For example, in many industries, manufactured articles are contaminated with processing solutions which must be removed prior to further processing or packaging.
Rinsing with a rinse liquid which will dissolve the first liquid and replace it with rinse liquid is the method most commonly encountered. Rinse water, for example, is frequently used to dissolve and remove water contaminated with plating salts from the surface of the article being plated. This system has decided disadvantages in that the rinse liquid, such as water, quickly also becomes contaminated with the first liquid and the surface cannot be completely cleaned due to the fact that residual rinse water containing the first liquid remains on the surface. Continuous discarding of the rinse liquid is not possible because it is expensive and presents a problem of pollution with the contaminating liquid. Rather than discard the contaminated rinse liquid, a second rinse system has been used to wash the surfaces after the first rinse. The second system will become contaminated by portions of first contaminated rinse liquid carried to the second system by the surface; a third rinse system can be set up to treat the contamination and, in this manner, a series of rinse systems have been employed. The contamination in each subsequent rinse system will be less than the contamination in each preceding system in this series; thus, the surface may be made as clean as desired by placing the required number of rinse systems in series. This is known as a cascade. It is not uncommon to encounter as many as 10 rinse systems in series which require a large amount of valuable space on a manufacturing line.
It has recently been proposed that rather than replacing the contaminating first liquid on the article surface with a less contaminating rinse liquid, the first liquid could be physically removed by washing with an immiscible liquid which would not absorb the first liquid and, therefore, would not become contaminated. Such a system does, in fact, physically remove a fairly large percentage of the contaminating first liquid held on the surface and does not replace it with a contaminated second liquid. The problem with the system, although an improvement over the cascade, is that all of the contaminating liquid is not physically removed and since there is no substitution, the portion of the contaminating liquid remaining is 100 percent of the concentration of the original contaminating liquid, thus a fairly large amount of contaminate remains on the surface.
It is also of course well known in the art that surface active agents, such as anionic, cationic and non-ionic surfactants can be added to a liquid which is miscible with the contaminating liquid so that the contaminating liquid forms an emulsion with the immiscible liquid. Such a system is unsatisfactory since the immiscible liquid rapidly becomes contaminated with emulsified contaminating liquid and in addition the surface active agent itself may often be an undesirable contaminate. Examples of such surface active agents are long chain alkyl trimethyl ammonium halides, neutralized alkyl phosphate esters, ethoxylated phenyl rings and natural soaps.
It is, therefore, an object of this invention to provide apparatus for efficiently and effectively removing a contaminating liquid from the surface of an article in a minimum of space. It is a further object of this invention to reduce waste by recovering a concentrated form of the contaminating liquid which may be recycled or otherwise used.
It is a further object of this invention to reduce pollution by liquid contaminates.
A fourth object of this invention is to provide apparatus capable of effectively and quickly removing contaminating liquids from article surfaces, without the use of surface active agents, which apparatus do not suffer the disadvantage of previously known apparatus used for this purpose.
A fifth object is to provide apparatus for collecting liquids removed from a process by an article and returning the liquid to the process in the proper amount to maintain continuous operation.
Further objects and advantages of the invention will be apparent from the following description.